This paper reports the composition and distribution of planktonic dinoflagellate inthe Southern Yellow Sea and its adjacent waters(32°~ 34°N,the west of 127°E)during the pe-riod from December 1997 to November 1978. 74 species belonging to 9 genera in families wereidentified, among which 71. 63 % were warm water species, 22. 97% eurythermic species,2. 7 % neritic species and 2. 7 % cold-water species. Seasonal variation of the total number of di-noflagellate shows that the highest peak was in July and the lo...